The heightened concern in recent years regarding energy problems has lead to considerable research with respect to energy conservation and savings in the field of energy sources. One specific area of interest is that of improving primary sources such as electrical batteries and, in particular, increasing the life of such batteries for both terrestrial and space applications.
Batteries used in space flight applications, and sealed batteries in particular, require close monitoring to make certain they are in good working condition and that all cells thereof are operative. Moreover, the monitoring or protective circuitry utilized for this purpose should be as compact and lightweight as possible while still being totally reliable. For example, the use of meter-relay type monitoring units in large quantities so as to protect each cell under test is impractical in terms of cost and space requirements. Further, in many instances, total protection has not been obtainable without the necessity of resorting to highly sophisticated computer equipment.
Reference is made to U.S. Pat. Nos. 3,305,754 (Oakes et al); 3,470,441 (Ford et al); 3,707,664 (Esh) and 3,806,906 (Young), for examples of battery charging and monitoring systems of interest. The Ford et al patent discloses an automatic formation cycler and controller for electrochemical cells wherein an electromechanical stepping switch is used to sequentially connect the individual cells into a testing circuit wherein the output of the cell is compared with the high and low voltage levels during charging and discharging. The switch sequentially routes voltage samples from each individual cell to a single voltage detector which thus monitors all of the cells in sequence. The Esh patent is an example of systems wherein individual voltage sensitive relays are used, the relays in this case being employed to monitor selected cells having a charge capacity significantly lower than the non-monitored cells. The Young patent discloses a system which indicates the failure to properly conduct current of any cell in each bridge of an electric power converter, while the Oaks et al patent discloses a charging apparatus for multi-cell batteries which employs a stepping switch scanner and meter relay unit to sense individual cell voltages.